Hinton D M, Bacon C W
USDA/ARS, Toxicology and Mycotoxin Research Unit, Russell Research Center, Athens, Georgia, USA.
Mycopathologia. 1995;129(2):117-25. doi: 10.1007/BF01103471.
The bacterium Enterobacter cloacae is presently used for biocontrol of postharvest diseases of fruits and vegetables and as a preplant seed treatment for suppression of damping-off. This bacterium has apparent affinities for several grass species, but it is not considered to be an endophyte. While screening corn for fungi and bacteria with potential for biocontrol of various corn diseases, the surface-sterilized kernels of one unknown Italian corn cultivar produced fungus-free corn seedlings with roots endophytically infected by E. cloacae. This paper describes the microscopic nature of E. cloacae RRC 101 with corn, and the in vitro control of Fusarium moniliforme and other fungi with this bacterium. Light and electron microscopy determined that this isolate of E. cloacae was biologically associated with corn seedling roots, where it was distributed intercellularly within the cortex and stele. This is a first report of a strain of this bacterium as an endophytic symbiont of roots. Following a topical application of E. cloacae to kernels, and upon germination this bacterium readily infected roots of two other corn cultivars. The bacterium was observed within the endosperm of germinating corn seedling, but germination was not affected. Further, the bacterium was isolated from leaves and stems of 3- to 6-week-old seedlings indicating that the above ground portions of corn were also colonized. There was no evidence of damage to cells of the root during a three to four week observation period. This bacterium was antagonistic to several isolates of the corn pathogen Fusarium moniliforme, and to two other species of fungi, all of which produce mycotoxins on corn.
阴沟肠杆菌目前被用于水果和蔬菜采后病害的生物防治，以及作为种植前种子处理以抑制猝倒病。这种细菌对几种禾本科植物有明显的亲和力，但它不被认为是内生菌。在筛选具有防治各种玉米病害潜力的真菌和细菌时，一种未知的意大利玉米品种的表面消毒种子产生了无菌的玉米幼苗，其根部被阴沟肠杆菌内生感染。本文描述了阴沟肠杆菌RRC 101与玉米的微观关系，以及该细菌对串珠镰刀菌和其他真菌的体外防治效果。光学显微镜和电子显微镜观察确定，这种阴沟肠杆菌菌株与玉米幼苗根部存在生物学关联，它分布在皮层和中柱的细胞间隙中。这是关于该细菌菌株作为根部内生共生体的首次报道。在将阴沟肠杆菌局部应用于种子后，种子发芽时该细菌很容易感染另外两个玉米品种的根部。在发芽的玉米幼苗胚乳中观察到了这种细菌，但发芽未受影响。此外，从3至6周龄幼苗的叶片和茎中分离出了该细菌，这表明玉米地上部分也被定殖。在三到四周的观察期内，没有证据表明根部细胞受到损伤。这种细菌对玉米病原菌串珠镰刀菌的几个分离株以及另外两种真菌具有拮抗作用，所有这些真菌都会在玉米上产生霉菌毒素。
